a. Field of Invention
The invention relates generally to improvements in pump dispensers, and more particularly to such pump dispensers having an improved spout valve assembly including an elastomeric one-way valve forming an air tight spout capable of quick shut-off of the discharge channel to prevent drying of product within the discharge channel.
b. Description of Related Art
The known manually actuated pump dispensers especially those designed for the dispensing of personal care products which may be in the form of pastes or gels, typically have both inlet and outlet check valves for respectively controlling the flow of liquid product into the pump chamber during each piston suction stroke and for controlling the outflow of the liquid product from the pump chamber during each piston compression stroke.
Such pump dispensers are advantageous in that they permit dispensing of products in a metered quantity over an extended period of use. However, extended use of many available pump dispensers often resulted in accumulation and drying of product at the dispenser head outlet or in the channel leading up to the outlet, which must be avoided from both an operational as well as hygienic point of view.
In order to address the drawbacks of product accumulation and drying with conventional pump dispensers, several valve designs have been proposed for sealing the channel leading up to the dispenser head outlet. U.S. Pat. No. 5,186,368 (hereinafter “the '368 Patent”) and U.S. Pat. No. 5,447,258 (hereinafter “the '258 Patent”) are exemplary of such a known pump dispensers. While the valve designs of the '368 and '258 Patents have improved upon conventional pump dispenser valve designs, as discussed below, these designs are nevertheless problematic in their own respect.
Specifically, referring to FIGS. 4 and 6 of the '368 Patent, the elastomer valve, referred to as a shutter 1, is mounted by telescoping it over a nipple (see FIG. 6) formed at the front end of pump head 2. Shutter 1 sealingly engages the nipple along the forward peripheral edge thereof as well as along the side periphery. Head 2 is disposed in sealed contact with side wall 11 of the shutter over a first surface which extends only over the inside of side wall 11, and the head is further disposed in sealed contact with the inside surface 210i of end wall 10. These assembly requirements enable shutter 1 to be sealingly engaged with the nipple.
As readily evident from the description of the '368 Patent valve design, the valve assembly is disadvantageous in that shutter 1 can easily dislodge over repeated use because of the ineffective mounting thereof on the nipple of pump head 2. This tendency to dislodge is especially of concern when the shutter is subjected to pasty product under high pressure during pumping. Further, the shutter cannot otherwise be strengthened for enhancing its mounting with the head since it is of a one-piece construction, and the shutter can only be rigidified to a certain degree since sufficient elasticity is needed for opening and closing the slit.
Turning now to the valve design of the '258 Patent, referring to FIG. 1 of the '258 Patent, the valve assembly includes first and second valve bodies 7, 11 partially retained within the dispenser head by stopper 22. Valve body 11 is specifically retained within the dispenser head by engaging part 8 disposed in contact with projection 3 a on one side of part 8 and stopper surface 22b on the other side thereof. Valves 7 and 11 operate by means of their engagement at location 10 (denoted opening part 10), where valve body 11 is disposed in sealing engagement with shaft 6 of valve 7. Thus, during downward pressing of head 20, product enters from pipe 2 into the space between valve 11 and shaft 6. When sufficient pressure is created, valve 11 expands radially to break the contact between end opening part 10 and shaft 6, and allow product to exit. Upon release of pressure on head 20, opening part 10 of valve 11 resumes contact with shaft 6 to seal the exit.
As readily evident from the description of the '258 Patent valve design, the valve assembly of the '258 Patent is disadvantageous in that it includes at least three components, namely valve bodies 7 and 11, and stopper 22 for effective sealing of the exit channel. Further, valve bodies 7 and 11, and stopper 22 are of relatively complicated designs. From a manufacturing point of view, for pump dispensers often made by the hundreds-of-thousands, the addition of a single component, as well as the preparation required for a relatively complicated mold can add significantly to the overall cost of the finished product. Further, as readily evident from the discussion above, while the valve assembly of the '258 Patent may provide adequate sealing of the outlet channel at early stages of dispenser operation, extended use of the '258 Patent pump dispenser invariably results in accumulation and drying of product at the dispenser head outlet due to product accumulation between opening part 10 and shaft 6.
In a similar manner as the '368 and '258 Patents, the spout valve designs of U.S. Pat. Nos. 6,497,346, 6,065,642 and 5,377,877 are problematic due to their complicated operation and assembly, and further due to the inadequate mounting thereof to the dispenser head.
It would therefore be of benefit to provide a pump dispenser having an improved elastomeric spout valve which both facilitates easier and more economical manufacture and assembly of the pump dispenser, which securely remains mounted to the dispenser head over the life of the pump dispenser for reducing or virtually eliminating the odds of the valve being dislodged from the dispenser head, regardless of pressures required for opening the valve slit, and which is robust in design and efficient in operation. It would also be of benefit to provide a spout valve which will quickly respond for sealing the discharge flow path during each piston suction stroke irrespective of the viscosity of the product being dispensed.